Nato will increase the number of its forces on high alert to over 300,000 from just 40,000, in the military alliance's "biggest overhaul" since the Cold War, General Secretary Jens Stoltenberg has said.
Mr Stoltenberg spoke ahead of a Nato summit that will set a new direction for the group in response to Russia’s invasion of Ukraine.During Tuesday's meeting in Madrid, Nato will decide on a new “strategic concept for a new security reality”, Mr Stoltenberg said.
He said that in response to Russia, "Nato will enhance our battlegroups in the eastern part of the alliance up to brigade-levels. “We will transform the Nato response force and increase the number of our high-readiness forces to well over 300,000."
Mr Stoltenberg added that Russia is "the most significant threat to our security".
Nato has released new figures which show that US allies in Europe, and Canada, have increased defence spending for an eighth consecutive year. “By the end of the year, they will have invested well over $ 350 billion extra since we agreed our defence investment pledge in 2014,” the general secretary said.
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His words came on the day that at least two people were killed and more than 20 were left injured after a shopping centre in Ukraine was struck by Russian missiles.
Ukrainian President Volodymyr Zelenskyy said that more than 1,000 people were in the shopping centre in Kremenchuk, Poltava, at the time of the attack.
This latest assault followed Russian missiles hitting the Ukrainian capital of Kyiv for the first time in weeks.
Also on Sunday, Moscow captured the city of Sievierodonetsk, its biggest victory since it seized Mariupol last month.
Boris Johnson will join allies at Tuesday's Nato meeting to agree a strengthened comprehensive assistance package for Ukraine, with deliveries of secure communications, anti-drone systems and fuel.
The alliance will also consider Sweden and Finland’s bids to join, applications made in response to the threat posed by Russia.
Turkish leader Recep Tayyip Erdogan has reservations about the plan, but he is due to hold talks with the leaders of the two countries in Madrid.
The Nato meeting will follow the G7 summit in Germany which was also dominated by talks on Ukraine.